ML20214A168
| ML20214A168 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 11/07/1986 |
| From: | Ainger K COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 2358K, NUDOCS 8611190273 | |
| Download: ML20214A168 (2) | |
Text
I_, o Commonwealth Edloon
- One First Nabonal Plaza. Chicago, IEncis
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l Address Reply to: Post Omco Box 767 Chicago, IEncis 60600 0767 November 7, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Byron Station Units 1 and 2 Preservice Inspection NRC Docket Nos. 50-454 and 50-455
Dear Mr. Denton:
This letter is to inform you that several shop-fabricated safety injection system pipe welds were inadvertently not examined during the Byron Units 1 and 2 preservice inspections. Location of the welds inside floor 4 -
penetrations makes their inspection impractical. However, relief from ASME code Section XI examination requirements is unnecessary since the i
examination of a significantly large sample of Class 2 welds was completed j
at Byron.
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During the Unit 2 preservice inspection, safety injection system weld C22B was discovered inside floor penetrations in pipe lines 2SIO6BA and 2SIO6BB. These lines are twenty-four inch diameter and run from the I
containment recirculation sump to the emergency core cooling system (ECCS).
Weld C22B is located between the containment isolation valve and the ECCS system. Subsequent review of the Unit 1 piping found corresponding weld C20B on line ISIO6BB. This weld was not identified during the Unit 1 l
preservice inspection. Since the Unit 1 and Unit 2 welds are inaccessible, they cannot be examined to Section XI requirements.
The Byron preservice inspections were performed to the requirements of lection XI 1977 Edition with addenda through Summer 1978 Addenda. Table l
IWC-2500-1, Examination Category C-F requires surface and volumetric l
exaaination of Class 2 circumferential piping welds with nominal wall thickness (t) over 0.5 inches. The examinations are to include 2.5t of the in'.ersecting longitudinal welds. Twenty-five percent of all non-exempt Class 2 welds are to be inspected prior to initial plant startup.
In an effort to increase the level of confidence in system integrity, Commonwealth Edison expanded the preservice inspection weld sample to include one-hundred percent of all non-exempt Class 2 welds. Code relief requests and preservice inspection (PSI) program plan notes identified all welds that could not be examined to Section XI requirements. The relief
-requests and notes accounted for only two percent of the Units 1 and 2 class 4
2 welds.
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8611190273 061107
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Mr. H. R. Denton November 7, 1986 PSI relief requests will not be provided for the safety injection system welds discussed above and their intersecting longitudinal welds. The Byron Class 2 weld inspection sample is substantially larger than the sample required by Section XI.
Furthermore, welds C20B and C22B are pipe-to-pipe configurations and are not a mandatory selection for inservice inspections.
Therefore,Section XI baseline examinations are unnecessary. The structural integrity of the welds is assured by acceptable ASME Section III radiographic examinations and hydrostatic tests as well as the high degree of toughness inherent in type 304 austenitic stainless steel. The PSI program plans for Byron Units 1 and 2 will be amended to incorporate this position and to add the welds to the isometric drawings.
Please direct any questions regarding this matter to this office.
One signed original and fifteen copies of this letter are provided for your information.
i Very truly yours, K. A. Ainger Nuclear Licensing Administrator 1m cc: Byron Resident Inspector I
2358K L
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